The objective of this study is to determine the safety and immunogenicity of an improved two-vial formulation of CHO cell-derived HIV-1 SF-2 rgp120 envelope vaccine formulated with MF59 adjuvant emulsion when administered to healthy HIV-1 uninfected volunteers. Prior formulations had suboptimal stability or were impractical (requiring storage at -70oC). Therefore, an improved formulation has been developed that is expected to be more practical and stable, to allow studies of this expanded vaccine candidate or analogous candidates designed for other geographic regions.